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Development of Economically Stabilized Phosphogypsum Composites for Saltwater Application

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An economic analysis of the production cost of PG:Class C fly ash:Portland Type II cement briquettes indicates that the most probable cost of 62%:35%:3% phosphogypsum: Class C fly ash: Portland Type II cement briquettes, based on a 4,500,000 ton per year production facility located near Tampa, Florida, would be $13.62. This estimated production cost does not give credit for the offset disposal cost, a cost that may range from a low of $1.50 per wet ton of PG to as much as $4 per wet ton. The former figure is judged to be a fairly reliable lower bound cost. However, the stated upper limit value is speculative. This cost would be highly dependent on the specific details of the disposal facility and the age of the facility. New disposal facilities will have to be constructed to meet liner and leachate and runoff collection facilities. Thus, the cost of PG disposal is expected to increase in the future. If a $4/ton offset disposal cost is accounted for in the production cost, the most probable cost of PGof PG briquette production would decrease to $10.86/ton.

The range of stated PG briquette production costs can be compared to a cost of $27-28/ton of granite riprap in Tampa, Florida. Considering the comparative cost of PG briquettes and granite, the cost of a granite armored geogrid-reinforced PG briquette composite protective structure will likely be competitive with a protective structure constructed solely of granite riprap. It is possible that the cost of producing the phosphogypsum briquettes may be reduced further by optimizing the type and quantity of admixtures used for production.